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FreeBSD-SA-15:11.bind                                       Security Advisory
                                                          The FreeBSD Project

Topic:          BIND resolver remote denial of service when validating

Category:       contrib
Module:         bind
Announced:      2015-07-07
Credits:        ISC
Affects:        FreeBSD 8.4 and FreeBSD 9.3.
Corrected:      2015-07-07 21:43:23 UTC (stable/9, 9.3-STABLE)
                2015-07-07 21:44:01 UTC (releng/9.3, 9.3-RELEASE-p19)
                2015-07-07 21:43:23 UTC (stable/8, 8.4-STABLE)
                2015-07-07 21:44:01 UTC (releng/8.4, 8.4-RELEASE-p33)
CVE Name:       CVE-2015-4620

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

BIND 9 is an implementation of the Domain Name System (DNS) protocol.
The named(8) daemon is an Internet Domain Name Server.  The libdns
library is a library of DNS protocol support functions.

II.  Problem Description

Due to a software defect, specially constructed zone data could cause
named(8) to crash with an assertion failure and rejecting the malformed
query when DNSSEC validation is enabled.

III. Impact

An attacker who can cause specific queries to be sent to a nameserver
could cause named(8) to crash, resulting in a denial of service.

IV.  Workaround

No workaround is available, but hosts not running named(8) are not
vulnerable.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 9.3]
# fetch https://security.FreeBSD.org/patches/SA-15:11/bind-9.patch
# fetch https://security.FreeBSD.org/patches/SA-15:11/bind-9.patch.asc
# gpg --verify bind-9.patch.asc

[FreeBSD 8.4]
# fetch https://security.FreeBSD.org/patches/SA-15:11/bind-8.patch
# fetch https://security.FreeBSD.org/patches/SA-15:11/bind-8.patch.asc
# gpg --verify bind-8.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart the applicable daemons, or reboot the system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/8/                                                         r285257
releng/8.4/                                                       r285258
stable/9/                                                         r285257
releng/9.3/                                                       r285258
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://kb.isc.org/article/AA-01267/>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-4620>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-15:11.bind.asc>
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